package algorithm.sort;

import java.util.Arrays;

public class SystemSort extends Common implements Sort {
    QuickSort sort = new QuickSort(ImplementType.DFS);

    @Override
    public void execute(int[] nums) {
        execute(nums, this.type);
    }

    @Override
    public void execute(int[] nums, ImplementType methodType) {
        Arrays.sort(nums);
        // sort(nums, 0, nums.length - 1, null, 0, 0);
    }

    static int QUICKSORT_THRESHOLD = 27;
    static int MAX_RUN_COUNT = 30000000;
    static int MAX_RUN_LENGTH = 110000000;

    void sort(int[] a, int left, int right, int[] work, int workBase, int workLen) {
        // Use Quicksort on small arrays
        if (right - left < QUICKSORT_THRESHOLD) {
            sort.quickSort(a, left, right);
            return;
        }

        /*
         * Index run[i] is the start of i-th run (ascending or descending
         * sequence).
         */
        int[] run = new int[MAX_RUN_COUNT + 1];
        int count = 0;
        run[0] = left;

        // Check if the array is nearly sorted
        for (int k = left; k < right; run[count] = k) {
            if (a[k] < a[k + 1]) { // ascending
                while (++k <= right && a[k - 1] <= a[k])
                    ;
            } else if (a[k] > a[k + 1]) { // descending
                while (++k <= right && a[k - 1] >= a[k])
                    ;
                for (int lo = run[count] - 1, hi = k; ++lo < --hi;) {
                    int t = a[lo];
                    a[lo] = a[hi];
                    a[hi] = t;
                }
            } else { // equal
                for (int m = MAX_RUN_LENGTH; ++k <= right && a[k - 1] == a[k];) {
                    if (--m == 0) {
                        sort.quickSort(a, left, right);
                        return;
                    }
                }
            }

            /*
             * The array is not highly structured, use Quicksort instead of
             * merge sort.
             */
            if (++count == MAX_RUN_COUNT) {
                sort.quickSort(a, left, right);
                return;
            }
        }

        // Check special cases
        // Implementation note: variable "right" is increased by 1.
        if (run[count] == right++) { // The last run contains one element
            run[++count] = right;
        } else if (count == 1) { // The array is already sorted
            return;
        }

        // Determine alternation base for merge
        byte odd = 0;
        for (int n = 1; (n <<= 1) < count; odd ^= 1)
            ;

        // Use or create temporary array b for merging
        int[] b; // temp array; alternates with a
        int ao, bo; // array offsets from 'left'
        int blen = right - left; // space needed for b
        if (work == null || workLen < blen || workBase + blen > work.length) {
            work = new int[blen];
            workBase = 0;
        }
        if (odd == 0) {
            System.arraycopy(a, left, work, workBase, blen);
            b = a;
            bo = 0;
            a = work;
            ao = workBase - left;
        } else {
            b = work;
            ao = 0;
            bo = workBase - left;
        }

        // Merging
        for (int last; count > 1; count = last) {
            for (int k = (last = 0) + 2; k <= count; k += 2) {
                int hi = run[k], mi = run[k - 1];
                for (int i = run[k - 2], p = i, q = mi; i < hi; ++i) {
                    if (q >= hi || p < mi && a[p + ao] <= a[q + ao]) {
                        b[i + bo] = a[p++ + ao];
                    } else {
                        b[i + bo] = a[q++ + ao];
                    }
                }
                run[++last] = hi;
            }
            if ((count & 1) != 0) {
                for (int i = right, lo = run[count - 1]; --i >= lo; b[i + bo] = a[i + ao])
                    ;
                run[++last] = right;
            }
            int[] t = a;
            a = b;
            b = t;
            int o = ao;
            ao = bo;
            bo = o;
        }
    }

}
